Description
Anodonthyla eximia is a miniaturized frog described from one adult male that was previously listed as an undescribed species in the Anodonthyla genus. The snout vent length of the holotype is 11.3 mm. The body is oblong, with a head that is narrower than the body width. The head is wider than long, and the head width measures at about 30% of the snout vent length. From a dorsal and lateral view, the snout is rounded. The nostrils are not protuberant, are directed laterally, and are located closer to the eyes than to the tip of the snout. The canthus rostralis is rounded and straight, while the loreal region is concave and vertical. The indistinct and round tympanum has a diameter that is about 46% of the eye diameter. The supratympanic fold is weak and goes straight from the posterior corner of the eye to the axilla. The skin of A. eximia is smooth, with no distinct dorsolateral folds (Scherz et al. 2019).

The forelimbs in A. eximia are relatively broad, and its length is about 40% the snout vent length. The outer metacarpal tubercle is single, small and indistinct while the inner metacarpal is large, distinct, and bulges outward strongly. The hands have no webbing, and all the fingers are short. The subarticular tubercles are single and indistinct. Anodonthyla eximia has a relative finger length of 1 < 2 = 4 < 3, with the first finger being highly reduced. Only the third finger is slightly expanded, the other fingers do not expand into discs. The hind limbs are robust, and its length is about 134% of the snout vent length. The tibiofibular length is around 39% of the snout vent length. The inner metatarsal tubercle is rounded and indistinguishable from the first toe, while the outer metatarsal tubercle is absent. The lateral metatarsalia is strongly connected and there is no webbing between toes. The first toe is strongly reduced to the point it is practically absent. The relative length of the other toes is 2 < 5 < 3 < 4 (Scherz et al. 2019).

Even the smallest of other Anodonthyla species (snout vent length of 15 mm) are larger than Anodonthyla eximia (snout vent length of 11.3 mm). Due to its small size, A. eximia is unlikely to be confused with other adult Anodonthyla species, however, it may be confused with juvenile frogs. Anodonthyla eximia can be distinguished from most other Madagascar miniature frogs by its large inner metacarpal tubercle that bulges outward strongly (a feature only present in males). Frogs in the genus Anilany also have a large inner metacarpal, however instead of having a cultriform shaped metacarpal, Anilany have a triangular shaped one (Scherz et al. 2019).

In alcohol, the dorsum is pale brown with a faint darker brown V-shaped stripe over the scapular region. The color of the dorsum fades to cream over the shanks, and this coloration continues to the venter. The legs have faint dark brown crossbands dorsally, especially on the shanks. From a lateral view, the head is dark brown with a distinct border between the dorsum and flank formed by the supratympanic fold. The chin is browner and darker than the venter, but lighter than the dorsum. Ventrally, the legs are translucent cream. In life, the color is more vibrant and the venter was colored slate grey with blue cream flecks (Scherz et al. 2019).

At the time of the species description, no variation could be determined because only one specimen has been observed (Scherz et al. 2019).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Madagascar

View distribution map in BerkeleyMapper.

The one A. eximia specimen collected was found in Ranomafana National Park, Maharira, in Madagascar (Scherz et al. 2019).

Life History, Abundance, Activity, and Special Behaviors
Anodonthyla eximia is a terrestrial species (Scherz et al. 2019).

Trends and Threats
As of 2022, A. eximia has not been assessed by the IUCN Red List. The species has a recommended status of "Data Deficient" from its species authority. It may be considered "Vulnerable" in the future as there are several other vulnerable species from Maharira (Scherz et al. 2019).

Comments
Maximum Likelihood and Bayesian Inference analyses using 16S and 12s rRNA mitochondrial genes found that A. eximia is sister to a clade consisting of Anodonthyla jeanbai, Anodonthyla moramora, Anodonthyla nigrigularis, Anodonthyla pollicarus, and Anodonthyla theoi (Tu et al. 2018, Scherz et al. 2019).

The species epithet, “eximia” comes from Latin, and is derived from the feminine form of the adjective “eximius”, meaning “remarkable or special”. This is in reference to its surprisingly small body size and terrestrial habits (Scherz et al. 2019).

References

Scherz, M. D., Hutter, C. R., Rakotoarison, A., Riemann, J. C., Rödel, M. O., Ndriantsoa, S. H., et al. (2019). "Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera." PLoS ONE, 14(3). [link]

Tu, N., Yang, M. H., Liang, D., Zhang, P. (2018). "A large-scale phylogeny of Microhylidae inferred from a combined dataset of 121 genes and 427 taxa." Science Direct, 126, 85-91. [link]

Species Account Citation: AmphibiaWeb 2022 Anodonthyla eximia <https://amphibiaweb.org/species/8991> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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